The present invention concerns an electronic typewriter comprising a platen roller and a carriage which is displaceable along the roller and on which are mounted a drive shaft, a rotatable character-carrying element, a transport member for displacement of the carriage and a selector shaft for selectively rotating the character-carrying element and selecting the characters to be typed. Also mounted on the carriage are one or more function devices for performing one or more functions associated with the typing of characters, a motion transmission unit having an input member connected in respect of rotary movement to the drive shaft and a first output member connected to the transport member, and transmission control means actuable into a transport state for connecting the drive shaft in respect of rotary movement to the first output member. The assembly includes an electric actuating motor for rotating the drive shaft and an electronic controlling arrangement for controlling the actuating motor, the transmission control means and the function device or devices.
A machine of that type uses a limited number of actuators such as motors and electromagnet units, and components for interfacing with the electronic controlling arrangement, in order drastically to reduce the overall cost of the machine.
An electronic typewriter with a reduced number of electromagnetic actuators is known from U.S. Pat. No. 4,239,400 assigned to Ing. C. Olivetti & C., SpA., in which the motion transmission unit is connected in respect of rotary movement to the selector shaft of the character-carrying element by means of a spring-and-ball type coupling. The transmission control means comprise a single actuation electromagnetic unit interfaced with the electronic controlling arrangement and a mechanical memory comprising a drum which is rotated by the drive shaft. The drum carries a series of selector rods which are slidable axially and which can be set by means of the actuating electromagnet, between a disengagement position and an engagement position, and the rods have radial teeth for acting on a series of couplings in response to the rotary movement of the drum. The couplings are interposed between the drive shaft and the devices to be activated and provide for execution of the various functions of the machine. Selection of the character is effected by stopping the selector shaft of the character-carrying element, by means of one of four stop levers which is suitably released by the selector rods while the drive shaft can continue to rotate for permitted disengagement of the spring-and-ball coupling. The actuating motor is capable of unidirectional motion and the mode of operation of the machine is of synchronous type. A machine of that type is slow and, while using a limited number of actuators, is costly by virtue of the complexity of the kinematic chain required for carrying out the selected functions.